In a previously filed U.S. patent application, Ser. No. 338,330, a facsimile receiver was described which uses a "drop on demand" type of ink jet printhead. This facsimile receiver prints images on plain paper. Printing on plain paper has obvious advantages over printing on thermal paper (which is the most common type of paper used in facsimile receivers), and the use of an ink jet type of printhead permits a receiver to be made at low cost. In order to keep up with the rate at which facsimile signals are normally received, the printhead cartridge must scan across the page at a relatively high speed, and must be reversed at the end of its travel with very little wasted time. These requirements create serious difficulties for prior art types of shuttle mechanisms.
Prior art types of printer shuttles are normally driven by either stepper motors or DC servo motors. At the end of each scan of the printhead, the motor is stopped and reversed to cause the printhead to scan across the page in the opposite direction. Such designs are satisfactory for applications where the moving masses are small and/or the turnaround accelerations required are low. However, as either the moving mass of the printhead assembly or the turnaround acceleration increases, the motor power required increases. Higher powered motors are, of course, physically larger and more expensive.
There are many applications where motor cost and size are important, yet the moving mass and/or low turnaround accelerations are high, as, for example, in a facsimile receiver using a drop on demand ink jet printhead. In such a receiver, the printhead assembly may weigh four ounces or more, and turnaround accelerations of the order of ten g may be required. These factors may result in a requirement for a larger motor than is desired in such a product. In addition, the inertial forces which result from reversing the printhead motion tend to cause undesirable movements of the printer itself.